Welch Allyn Diatek 600 User manual

Diatek®Model 600 Thermometer
Technical Manual
Thermo Menu
Operation Manual

Model 600
© 1996 by Diatek Instruments, Inc., A Welch Allyn Company. All rights reserved. No part of this manual may be reproduced
or transmitted in any form or by any means, electronic or mechanical, including photocopy, without prior consent in writing
from Diatek. Printed in the U.S.A.
Diatek is a trademark of Diatek Instruments, Inc. All rights reserved.

Technical Manual
Model 600 1
TABLE OF CONTENTS
WARRANTY.............................................................................................................................3
MODEL 600 OPERATIONAL CHARACTERISTICS................................................................4
Normal Mode.........................................................................................................................4
Monitor Mode.........................................................................................................................4
Pulse Timer............................................................................................................................4
Backlight................................................................................................................................4
Error Indicators......................................................................................................................5
Broken Probe .................................................................................................................................5
Low Battery ....................................................................................................................................5
Instrument Malfunction...................................................................................................................5
Self-Tests...............................................................................................................................5
Battery Installation Display Test.............................................................................................5
Thermometer Startup Tests...................................................................................................5
Display and Horn Test....................................................................................................................5
Internal Calibration Test .................................................................................................................5
Internal Microprocessor Test..........................................................................................................6
Battery Life.............................................................................................................................6
Shelf Life........................................................................................................................................6
Temperature Taking Without Backlight...........................................................................................6
Temperature Taking With Backlight ...............................................................................................6
C/F Mode Switch....................................................................................................................6
Normal/Monitor Mode Switch.................................................................................................6
MODEL 600 THEORY OF OPERATION..................................................................................7
Technical Overview................................................................................................................7
Temperature Measurement and Display................................................................................7
Probe Temperature Measurement.........................................................................................8
Monitor Mode Operation........................................................................................................8
Normal Mode Operation ........................................................................................................8
SELF TESTS.........................................................................................................................9
Internal Calibration Test .................................................................................................................9
Internal Microprocessor Memory Test.............................................................................................9
Broken Probe Test .........................................................................................................................9
DISPLAY................................................................................................................................9
Display Voltage Reference.............................................................................................................9
Display............................................................................................................................................9
Horn ...............................................................................................................................................9
Backlight.........................................................................................................................................9
Power Consumption ............................................................................................................10
Low Battery Detection..........................................................................................................10
Pulse Timer Operation.........................................................................................................10
SPECIFICATIONS..................................................................................................................18

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OPERATING INSTRUCTIONS...............................................................................................19
Set-up Procedure.................................................................................................................19
Preparation for temperature measurement:.........................................................................19
Normal Mode Operation ......................................................................................................19
Oral Temperature Measurement ..................................................................................................19
Rectal Temperature Measurement...............................................................................................20
Monitor Mode Operation......................................................................................................20
Backlight Operation .............................................................................................................20
Pulse Timer..........................................................................................................................20
°F/°C Conversion.................................................................................................................20
Error Indicators....................................................................................................................21
Broken Probe ...............................................................................................................................21
Low Batteries................................................................................................................................21
Probe Position Error.....................................................................................................................21
Malfunction...................................................................................................................................21
Self Tests.............................................................................................................................21
Initial Power Up Display................................................................................................................21
Calibration Check.........................................................................................................................21
Microprocessor Self Check...........................................................................................................22
Cleaning and Sterilization....................................................................................................22
Battery Replacement...........................................................................................................22
Calibration Key Procedure...................................................................................................22
Test Procedure.............................................................................................................................23
M9600 Procedure................................................................................................................24
MODEL 600 TROUBLESHOOTING.......................................................................................24
PARTS LIST (units with serial numbers equal to or greater than 193309) ......................26
PARTS LIST (units with serial numbers less than 193309)...............................................27
RECOMMENDED SPARE PARTS FOR MODEL 600 ...........................................................28
MODEL 600 PREVENTATIVE MAINTENANCE ....................................................................29
TABLE OF FIGURES
Figure 1 - Block Diagram........................................................................................................11
Figure 2 - Schematic...............................................................................................................12
Figure 3 - Schematic (earlier serial numbers).........................................................................13
Figure 4 - Printed Circuit Board Component Layout...............................................................14
Figure 5 - Final Assembly.......................................................................................................15
Figure 6 - Operating Controls and Components.....................................................................17

Technical Manual
Model 600 3
WARRANTY
1-YEAR LIMITED WARRANTY ON NEW INSTRUMENTS: Instrumentation purchased new from
Diatek Instruments, Inc. (Diatek) is warranted to be free from original defects in material and
workmanship under normal use and service for a period of one year from the date of first shipment
from Diatek. This warranty shall be fulfilled by Diatek or its authorized representative repairing or
replacing at Diatek's discretion, any such defect, free of charge for parts and labor.
Diatek should be notified via telephone of any defective product and the item should be immediately
returned, securely packaged and postage prepaid to Diatek. Loss or damage in shipment shall be at
purchaser's risk.
Diatek will not be responsible for loss associated with the use of any Diatek product that (1) has had
the serial number defaced, (2) has been repaired by anyone other than an authorized Diatek Service
Representative, (3) has been altered, or (4) has been used in a manner other than in accordance with
instructions.
The information in this manual has been carefully reviewed and is believed to be accurate; however, no
responsibility is assumed for inaccuracies. Furthermore, this information does not convey to the
purchaser of Welch Allyn or Diatek devices any license under the patent rights to the manufacturer.

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4 Model 600
MODEL 600 OPERATIONAL CHARACTERISTICS
The Diatek Model 600 Digital Thermometer is a portable instrument for measuring patient
temperatures over the 84°F to 108°F (28.9°C to 42.2°C) range. The Model 600 features an LCD
readout with backlight, interchangeable probes, disposable prove covers, disposable batteries with a
capacity for up to 45,000 temperatures, automatic power shutdown, both normal and monitor modes of
operation and self-calibration/test capability.
Normal Mode
Removal of the probe automatically turns on the Model 600 and places it in the predict mode when
selected by the normal/monitor slide switch. All segments of the display except the pulse timer are
lighted simultaneously for 6 seconds as a display test and the horn is tested for 0.1 seconds. The
display will read 84.0 (28.9) with the down arrow on until the probe exceeds that temperature and will
ten display a rising temperature for about 30 seconds.
When the readout has stabilized, the horn will sound for 1 second, the “F” or “C” symbol will light and
the display will remain fixed indicating the end of the temperature taking cycle. The displayed
temperature will be the actual probe temperature plus a computed correction factor. The probe
temperature is sensed about 4 seconds from turn on to correct for ambient probe temperature
variations. If the temperature measurement cycle is not completed within 5 minutes from turn on, the
thermometer will turn off at that time. A temperature in excess of 108°F (42.2°C) will cause an error
condition to be indicated by the horn beeping twice every 10 seconds and the up arrow blinking. Five
minutes of this error condition causes the thermometer to turn off. Returning the probe to its holder
and then removing it will restart the thermometer.
Note: The normal mode display is peak reading and will not read down.
Monitor Mode
Removal of the probe automatically turns on the Model 600 and places it in the monitor mode when
selected by the normal/monitor slide switch. All segments of the display except the pulse timer are
lighted simultaneously for 6 seconds as a display test and the horn is tested for 0.1 seconds. The
display will then indicate the actual probe temperature, updating every 1.5 seconds as long as it
remains within the 84°F to 108°F (28.9°C to 42.2°C) range, and will show the appropriate up or down
arrow when outside this range. Five minutes of operation outside the operating range will cause the
thermometer to turn off.
Pulse Timer
Pressing the pulse timer switch at any time causes the 30 second clock type display to start. One
additional segment is turned on each second until 30 seconds has been reached at which time the
timer display goes blank. The horn sounds for 0.1 second at 0,15, and 30 seconds. Pressing the timer
switch while the timer is running causes the timer to restart. The switch will not respond if pressed
sooner than 1.5 seconds since the last timer activation.
Backlight
The backlight is activated as long as the backlight switch is pressed and the thermometer function is
active. In the predict mode, activating the backlight any time prior to the end of the temperature taking
cycle will cause the backlight to turn on for 5 seconds when the final temperature has been reached
and the horn sounds. No backlight is available when only the pulse timer is in use.

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Model 600 5
Error Indicators
Probe Position Error—During normal mode operation the visual probe position error indicator will be
displayed as long as tissue contact is broken and the probe temperature is falling. This display
indicates that a condition exists which may not provide accurate temperatures. The error indicator does
not affect the temperature taking cycle in any way.
No temperatures may be taken when any of the following error conditions exist:
Broken Probe
A probe error will be indicated if the probe circuit is open (below 10° greater than 60,000 ohms) or
shorted (above 150° F or less than 2,000 ohms). The horn sounds a double beep repeating every 10
seconds with the probe error display flashing. The unit will shut off automatically after 5 minutes of
error indication. The error will be detected any time during predict or monitor mode operation.
Low Battery
A low battery condition exists when the battery voltage drops to approximately 3.0 volts. A low battery
indication may occur any time during monitor mode operations but only at the start of a predict mode
temperature. If a low battery condition exists prior to starting the pulse timer, the low battery error will
be displayed when the timer is started and any normal mode temperature in progress will abort at that
time. The low battery error displays a flashing symbol with a double horn beep sounding every 10
seconds. The unit will shut off automatically after five minutes of error indication.
Instrument Malfunction
A malfunction error will be indicated if either the internal calibration self-test or the internal
microprocessor self-test fails. The malfunction indicator flashes with a double horn beep sounding
every 10 seconds. The thermometer will automatically shut off after five minutes of error indication.
Self-Tests
Battery Installation Display Test
Immediately following the installation of batteries into the Model 600, a one time only display test is
provided. All segments of the entire display (including the pulse timer and error indicators) are
sequentially lighted for 0.4 seconds. The entire test takes 25 seconds and must occur prior to starting
any temperature or timer functions.
Thermometer Startup Tests
Display and Horn Test
Each time the probe is removed from its holder all display segments (except for the pulse timer) are
lighted for 6 seconds as a visual display test. During the display test the horn sounds for 0.1 second.
Internal Calibration Test
During each thermometer startup display test a precision resistor is used to check the thermometer
calibration at 100.5°F (38.1°C). A failure of the thermometer to measure the calibration resistor within
±0.2°F will cause the malfunction error to flash, the horn will sound with a double beep every 10

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6 Model 600
seconds and no temperature measurement will be allowed. The thermometer will automatically shut off
after 5 minutes of the error display.
Internal Microprocessor Test
During each thermometer display test a check sum of all program memory is calculated and compared
against a reference stored in the program memory. An error in the check sum will cause the
malfunction error to flash, the horn will sound with a double beep every 10 seconds, and no
temperature measurement will be allowed. The thermometer will shut off after 5 minutes of the error
display.
Battery Life
Shelf Life
The shelf life of carbon zinc chloride or alkaline batteries should be at least three years when stored at
70°F. The storage life degrades rapidly with increased temperature.
Temperature Taking Without Backlight
The Model 600 should operate continuously for about 2,000 hours when the backlight is not used. If an
operating time of 2 minutes per temperature is assumed then the potential number of temperatures
that can be taken should be about 2,000 hours @ 30 temperatures/hour = 60,000 temperatures.
Temperature Taking With Backlight
The backlight uses about 20 times more power than the rest of the thermometer. If 20 seconds of
backlight usage is assumed for each temperature taken then the number of temperatures that can be
taken should be about 17,300 temperatures.
C/F Mode Switch
The display mode may be changed between Fahrenheit and Celsius at any time prior to, during, or
after taking a temperature by activating the C/F slide switch. The numbers will change as the switch is
activated, however, the C/F indicator is only visible at the end of a normal mode temperature.
Normal/Monitor Mode Switch
The selection of normal or monitor mode operation should be made prior to turning on the thermometer
by setting the normal monitor switch to the desired position. Once the thermometer has been turned
on, a change from normal to monitor mode may be made at any time, however, a change from monitor
to normal will cause the horn to beep twice and the thermometer to shut off. This error indication and
shut off prevents a normal mode temperature from being started with the probe already in place.

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Model 600 7
MODEL 600 THEORY OF OPERATION
Note: Refer to Model 600 Thermometer Block Diagram and Model 600 Schematic Diagram.
Technical Overview
The heart of the Model 600 is comprised of two custom integrated circuits which provide the
microprocessor and analog circuit functions. All control and display functions are governed by the
microprocessor (U2) and all analog interfacing to the microprocessor, probe, horn and backlight is
provided by U1. Probe resistance measurements are made by ratioing pulse widths generated by
sequentially switching in two calibration resistors and the probe thermistor. These pulse widths are
measured by the microprocessor which calculates the probe resistance. The actual probe temperature
is then calculated from the probe resistance.
During monitor mode operation, the actual probe temperature appears directly on the liquid crystal
display which is driven by the integral LCD driver on the microprocessor.
During normal mode operation, the shape of the rising temperature curve is monitored and a
continuously computed correction factor is added to the actual probe temperature. The normal mode
temperature cycle is terminated when the predicted temperature remains stable.
All switch inputs are monitored by the microprocessor which in turn activates the required functions.
Inputs to the microprocessor are A/D output pulse widths, switches, low battery detection, power on
reset, microprocessor clock and interval timer clock.
Outputs from the microprocessor control the display, analog IC and display power, backlight, horn and
calibration resistor selection.
To extend battery life, the power to both the analog lC (U1) and the LCD reference are turned off and
the microprocessor is put to sleep when possible.
Power to the thermometer is always connected and is not turned on and off by the probe or pulse
switch functions.
Temperature Measurement and Display
When batteries are installed in the thermometer, C4 and RN1-B provide a power on reset pulse to the
microprocessor (U2-56). C3 and RN1-A set the microprocessor clock frequency at approximately 200
kHz. Following the high going reset pulse, the microprocessor initiates the power on display test which
causes display segments (DS1 ) to be sequentially lighted for 0.4 seconds and then extinguished. After
the completion of the display test which lasts approximately 25 seconds, the microprocessor then goes
into a sleep mode awaking 8 times per second to test the probe switch S1. If the probe is in the
thermometer (S1 open) or the probe is disconnected, then the microprocessor returns to sleep for
another 1/8 of a second. The pulse timer switch (S5) is connected to an interrupt input on the
microprocessor (U2-63) and will wake up the microprocessor and start the 30 second pulse timer.
In the sleep mode and even when only the pulse timer is active, the 200 kHz clock (U2-59) will be seen
to turn on for about 2 milliseconds every 1/8 of a second. If when tested, the probe switch circuit is
found to be active, the microprocessor turns on display power by setting U2-10 low and initiates a 6
second display test which turns on all display segments except the 30 second pulse timer
simultaneously. During the display test the following events take place.
1. The A/D power control line (U2-3) is set high by the microprocessor to turn on the power to U1.

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2. The low battery detector output (Ul-9) is tested by the microprocessor. A low logic level on Ul-9
indicates a low battery condition (less than 3.0 volts).
3. The horn drive signal (U2-11) goes high activating the horn test for 0.1 second.
4. The backlight switch, normal/monitor switch and F/C switches are tested by the microprocessor.
5. A calibration cycle is performed.
6. The calibration test is performed.
7. The microprocessor memory test is performed.
8. The probe resistance is tested for an open or shorted condition.
Following the events which take place during the display test, a continuous monitor mode temperature
measurement or a predict mode temperature taking cycle is started.
Probe Temperature Measurement
Q3-Q6, Q8, R3-R5, R-16, C2 and U1 comprise a unique resistance to pulse width conversion circuit
which allows any one of 4 resistance’s to be measured by the microprocessor. The circuit allows the
microprocessor to select precision resistors with equivalent temperatures at opposite ends of the
temperature measurement range and measure their relative pulse widths.
The microprocessor sets U2- 16 to 19 high as required to select the appropriate resistance to be
measured. R3 provides a pulse width calibration at 93.2 °F, R5 provides calibration at 106.9 °F and R3
is used for a calibration test at 100.5 °F. A ratiometeric calculation is used to compute the probe
resistance from its pulse width relative to those provided by R3 and R5. The accuracy of each
calibration resistor is .05 °F. A resistance to pulse width conversion is initiated by the microprocessor
setting U2-64 high for approximately 0.5 seconds with the appropriate FET switch selected sometime
within that period. U2-64 is then set low and the time from this transition until the A/D output (U1-2)
goes high is measured by the microprocessor. The crystal X1 provides the time base for the pulse
width measurements. The probe temperature is computed using the probe resistance value obtained
from the ratiometeric pulse width calculations.
Monitor Mode Operation
In the monitor mode a new probe temperature measurement is completed every 1.5 seconds and a
new calibration cycle is completed every 3 seconds. The computed probe temperature is displayed
directly on the liquid crystal display and will follow both upward and downward movement.
Normal Mode Operation
In the normal mode. a new probe temperature measurement is completed every 1.5 seconds. At least
one calibration cycle is performed at the start of a predict cycle and continue every 3 seconds until the
probe temperature rises above 84.0 °F. The calibration cycle is stopped at this point to reduce
quantizing errors associated with the measurement of the slowly changing probe temperature.
The normal mode displayed temperature is the sum of the actual probe temperature and a computed
correction factor which is based on the shape of the changing temperature curve at that point in time.
The values of the correction factor can vary from 0 °F to 2.3 °F with a typical value when the horn
sounds of about 1 °F. During the display test prior to starting a normal mode temperature cycle, the
ambient temperature of the probe is measured and is used in the correction factor computation to
adjust for differing probe starting conditions. The normal mode display is peak reading and therefore
the highest temperature is displayed even though the present predicted probe temperature may drop.

Technical Manual
Model 600 9
The normal mode temperature cycle is terminated when the predicted temperature remains stable for
several seconds.
SELF TESTS
Internal Calibration Test
The calibration test is performed only once during a temperature taking cycle and occurs during the
display test. Upon completion of the first calibration cycle, the resistance of R4 is measured and
compared against limits stored in the microprocessor memory. The specified limits are 5740 and 5780
ohms. If the resistance calculated by the microprocessor when the pulse width of R4 is measured does
not fall within these limits, the malfunction error is displayed.
Internal Microprocessor Memory Test
The microprocessor memory test is performed only once during a temperature taking cycle and occurs
during the display test. Each 8 bit byte of program memory is divided into two 4 bit nibbles which are
summed. The total sum of all nibbles and a special check sum compensation nibble must be O or the
malfunction error is displayed.
Broken Probe Test
Each probe resistance sample that is taken is checked to see that it lies between 2000 and 60,000
ohms. A resistance value outside of these limits will cause a broken probe error to be displayed.
DISPLAY
Display Voltage Reference
Diodes CR2-CR6. Q7, R61 and R7 create the display voltage references of about (V+)—1 volt at U2-
25 (V+)—2 volts at U2-24 and (V+)—3 volts at U2-23.
Display
The liquid crystal display is of the 4 backplane multiplexed type (quadraplex), requires a regulated
operating voltage, and is driven directly by the microprocessor.
Horn
The microprocessor provides a control signal to U1-3 which is the feedback input for the horn driver
contained in U1. The horn driver output (U1-l) drives the horn (H1) at its self resonant frequency of
about 6 kHz.
Backlight
The microprocessor activates the backlight by setting U2-4 high. This signal is inverted and buffered
and reappears at U1-13 going low. A low level on U1-13 turns on the backlight inverter circuit
consisting of Q1, Q2, R1, R2, C5 and T1. The inverter supplies an AC voltage of about 80 volts and
300 Hz to the Electroluminescent panel BP1. CR7 blocks negative voltage spikes from entering U1-13.

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10 Model 600
Power Consumption
Without the thermometer or pulse timer active the average battery current should be under 50
microamperes. When the thermometer function is active the average battery current should be about 1
milliamp.
Maximum battery current with the backlight on should be about 25 milliamperes.
Low Battery Detection
When the battery voltage is reduced to 3.2 volts, Ul-9 goes low indicating a low battery condition to the
microprocessor which in turn causes the low battery indication to be displayed.
Pulse Timer Operation
Pressing the pulse timer switch activates the microprocessor interrupt to (U2-63) starting the pulse
timer display. The pulse timer input is independent from the temperature taking functions and may be
activated at any time. Starting the pulse timer causes the microprocessor to turn on the horn for 0.1
seconds at 0, 15 and 30 seconds and light one additional clock segment each second until the display
is fully lighted at 30 seconds at which time the clock display blanks. The timer cannot be restarted for
1.5 seconds following the last press of the timer switch but may be restarted at any later time.

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Model 600 11
Figure 1 - Block Diagram

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12 Model 600
Figure 2 - Schematic

Technical Manual
Model 600 13
Figure 3 - Schematic (earlier serial numbers)

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14 Model 600
Figure 4 - Printed Circuit Board Component Layout

Technical Manual
Model 600 15
Figure 5 - Final Assembly

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16 Model 600

Technical Manual
Model 600 17
Figure 6 - Operating Controls and Components

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18 Model 600
SPECIFICATIONS
Range: Normal and monitor modes
28.9°C to 42.2°C
84.0 °F to 108.0 °F
Accuracy: ±0.1 °C, ±0.2 °F (when tested in a calibrated water bath)
Battery Capacity: disposable batteries
three type AA cells
up to 1000 hours of continuous use
Dimensions: length 6.25 inches (159mm); width 3.7 inches (94mm); height 2.4 inches
(61mm)
weight: 10.5 ounces (298 grams)
case material: ABS Cycolac “T” grade plastic
Visual and Audible
Indicators: digital temperature display
30 second pulse and respiration timer
instrument malfunction
broken probe
probe position
low battery
out of range temperature